Methods and electrolytes for depositing nickel and cobalt



United States Patent 3,093,557 METHODS AND ELECTROLYTES FOR DEPOSIT- INGNICKEL AND COBALT Richard P'- Cope, JL, Wilkiusburg, and John R. Drobne,

Munhall, Pa.,. assignorsv to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvama No Drawing. Filed Aug. 25,196.1, Ser. No. 133,800 14 Claims. (Cl. 204 -43) This invention relatesto bright metal electroplating methods and novel electrolytecompositions. More particularly, this invention relates to anelectrolyte from which bright nickel, cobalt and alloys of nickel-cobaltmay be electrodeposited.

Many compounds are known to be useful as additives to nickel, cobalt andnickel-cobalt alloy electrolytes. Aliphatic nitriles are among thecompounds that have been usedf These nitr-iles havebeenusedincon-junct-ion with well known organic sulfon=compounds knownin the art as carriers or regulators. Examples of systemsincorporating'nitriles in conjunction with organic sulfon-compounds ascarriers or regulators are disclosed in US. Patent 2,882,- 208 and US.Patent 2,524,010. The known n-itrile brighteners are volatile, poisonousliquids. They are extremely hazardous because they are nerve poisonsthat migrate through the skin, possibly effecting permanent braindamage. Not only are such compounds dangerous to handle, but manytwillboil out of plating baths at high tern peratures. The hazards'ofexposure to such vapors is obvious.

Accordingly, it is the general object of this invention to provide anovel system for bright nickel plating incorporating soluble soliddicyano compounds as 'brighteners.

It is a more particular object of this invention to provide a system forbright nickel, cobalt, and nickel-cobalt alloy plating incorporatingsoluble solid dicyano compounds which may be safely handled.

We have discovered a method of improving electrolytes of nickel, cobaltand nickel-cobalt alloys by the incorporation therein of a predeterminedamount of a series of dicyano' compounds that are solid at roomtemperature and are highly effective brighteners. Since they are solids,the corn-pounds are safer to handle than the volatile nitrile liquids.While these compounds cannot be ingested without possible seriousconsequences, the problemv of inhalation is essentially eliminated.Higher plating bath temperatures may be employed without generatinghazardous vapors. Higher temperatures permit the use of higher currentdensities;

Using these compounds in the hereinafter described electrolytes, it ispossible to electrodeposit bright coatings which are fairly ductileandlevel. The compounds are selected from the group consisting ofdicyanoketeneethyleneacetal and compounds having the formula:

. NEG R wherein R is a radical selected from at least one of the groupconsisting of NH 0R and NHR in which R is an aliphatic monovalenthydroc-arbonradical with one to three carbon atoms. The R substituentsneed not be the same in a given compound. The brighteners of thisinvention may be used with sulfur-containing carriers or regulatorsknown in the art. The aliphatic monovalent hydrocarbon radical R islimited to those radicals having from one to three carbon atoms.Radicals with a greater number ofcarbon atoms ordinarily result incompounds that are relatively insoluble in the electrolyte. It is ap-3,093,557 Patented J mm 1 1, 1963 ice parent, then, that all soliddicyanoketene compounds cannot be satisfactorily employed in theinvention.

The following series of compounds used in Examples I to IV hereinafterwas produced as indicated:

(a) The d-icyanoketeneethyleneacetal used in Example- I was prepared asfollows:

12.89 grams of tetracyanoethylene, two grams of urea as a catalyst, and24 ml. of ethylene glycol were heated on a steam bath until thetetracyanoethylene went into solution. The product was poured into ml.of ice water, filtered and recrystallized in an alcohol-water solution.The resulting fluffy light brown needles had a melting point of 112,113C.

(b) The. 1,1-dicyanos2,2 diaminoethylene used in Example II was preparedas follows:

6.7 grams of d-icyanoketeneethyleneacetal and 21.5 of concentratedammonia were refluxed for ten minutes. The product was permitted tostand overnight. The light lzarowr3 material recovered had a meltingpoint of 247- (c) The 1,1-dicyano-2,Z-diethoxyethylene used in ExampleIII was prepared as follows:

' 6.4 grams of tetracyanoethylene, 3 gram-s of urea as a catalyst and 50ml. of alcohol were heated ona steam bath for 20 minutes. The productwas cooled and then evaporated to 25' m1. at room temperature by blowingair across it. Then, 25 ml. of water Was added. The material was cooled,filtered and air dried. The white crystals produced had a melting pointof 54 to 56 C.

(d) The l,l-dicyano-Z,2-di-n-propylamine used in EX- ample IV wasprepared as follows:

6.7 grams of dicyanoketeneethyleneacetal dissolved in, 50 ml. of Waterand 10 ml. of n-propylamine were refluxed for 20 minutes. The productwas cooled to 0 C. and then filtered. A light brown precipitateresulted.

' The foregoing compounds are incorporated into plating baths asillustrated by the following specific, examples:

The bath is agitated with air. A highly bright, leveled and fairlyductile nickel deposit is obtained. The deposit 1sv bright in thecurrent density range from 10 to 250 amps/sq. ft. 1

Example 11- Cobalt sulfate, CoSO .7I-I O oz ./gal. 67 Sodium chloride,NaCl ..oz./gal. 2 Boric acid -c "oz/gal.-- 6.1,1-dicyano-2,2-diaminoethy1ene ;oz./gal., .01 Napthalene trisulfonicacid oz./gal... 1 Sodium 2-ethylhexyl sulfate oz./gal; 0.003 pH a f 4.5.Temperature F..'. i 120,

Agitation is achieved with cathode rod movement. A bright'leveled andfairly ductile deposit is obtained. The deposit is bright in the currentdensity range from 10 to 200 amps/sq. ft.

Example III NiCl- .6H O oz/gal.-- 10-30 H BO oz./ gal.-- .0-8-1,1-dicyano-Z,Z-diethoxyethylene oz./gal.;.. 0.01 Sodium styrenesulfonate oz gal. 0.01 Sodium lauryl sulfate ..oz./gal. 0.02 pH A I 3.5Temperature F 3 Agitation is achieved with cathode rod movement. Abright, leveled and ductile nickel deposit is obtained. The deposit isbright in the current density range of from to 150 amps/sq. ft.

l,l-dicyano-2,2-n-propylaminoethylene oZ./ga1. 0.001

8-acetamido-3,6-naphthalene disulfonate oz./gal. 2.0 pH 4.0 TemperatureF 150 Thebath is agitated with air. A bright nickel cobalt alloy depositis obtained. The deposit is bright in the current density range of from10 to 100 amps/sq. ft. In a similar way dimethoxy and dipropoxycompounds may be employed in the bath to replace the 1,1-dicyano- 2,2-diethoxyethylene.

The chloride of the electrolyte can be added as sodium chloride ormagnesium chloride. The sodium lauryl sulfate and sodium 2-ethyl hexylsulfate are well known wetting agents. Other wetting agents, known inthe art, may also be used in the baths.

The brightener components of this invention may also be incorporatedinto sulfamate and fiuoroborate plating baths, as well as those in theexamples, with equally good results. Bright plate may be obtained withbrightener compounds of this invention at concentrations in the range offrom 0.0005 to 0.05 oz./gal., in any of the foregoing experimentalelectrolytes.

Nickel-containing electrolytes suitable for electroplating nickel may beany acidic nickel salt solutions employed in the art for plating. It hasbeen found that the single or double nickel sulfate and nickel chloridesalts alone or in any combination may be employed. Other platable nickelsalts may be employed. The nickel plating baths are acidic, having a pHof from 0.5 to 6. In many cases buffers, such as boric acid, and otheraddition agents, may be present; in some cases marked benefical resultsare obtained when they are present. Examples of suitable addition agentsare organic sulfonates, such as naphthalene-1,5-disulfonic acid,ammonium sulfate, formaldehyde, nickel formate, sodium sulfate, sodiumlauryl sulfate, and ammonium chloride. Gum arabic and gum tragacanth andthe like may be present. If required, additions of hydrochloric orsulfuric acid may be made to the electrolytes.

For plating cobalt, the electrolyte may contain cobalt sulfate, cobaltchloride or mixtures thereof. Similar addition agents to those used withnickel electrolytes may be added to these solutions to advantage. The pHof the aqueous electrolytes may be from 0.5 to 6.

In plating nickel-cobalt alloys, mixtures of nickel salts and cobaltsalts are dissolved in the aqueous electrolyte. The baths have a pHrange of from 0.5 to 6. For alloy plating cobalt-nickel anodes are used.Particularly useful alloys are those containing from 80% to 97% nickelby weight and 20% to 3% cobalt by weight. However, alloys containinggreater amounts of cobalt may be readily plated. Alloys of nickel and/orcobalt and iron and iron alone may also be deposited from electrolytescontaining the additives described heretofore with similar advantage.

The compounds of this invention are particularly valuable in fast cyclereverse current plating baths. Lower concentrations of the brightenersmay be used in the fast cycle reverse current processes with excellentresults. A desirable periodic reverse current process is described inUS. Patent No. 2,470,775 to Jernstedt et al., assigned to the assigneeof the instant application. A periodic reverse current in which thecathodic portion of the cycle, applied to the member being plated withnickel, is two seconds or less or, preferably, less than one-half secondand an anodic portion of the cycle from one-half to one-twenty fifth ofthe cathodic portion with the current densities adjusted so that theanodic portion of the cycle applies from 4% to 60% of the coulombs ofcurrent applied during the cathodic portion of the cycle, will produceexcellent electrodeposits. The cycles may be reduced in time to aslittle as A of a second cathodic period and of a second anodic periodwith benefit. Below an anodic time period of about second, the deplatingis not effective enough to give the full advantage of periodic reversecurrent plating.

The following examples illustrate the results obtained with thebrightener compositions of this invention in the periodic reversecurrent process:

A periodic reverse current cycle is used with periods of 1s second andsecond for the cathodic and anodic portions, respectively. Brightductile and leveled electrodeposits of nickel are obtained at from 10 to200 amps/sq. ft.

A periodic reverse current cycle is used with periods of second andsecond for the cathodic and anodic portions, respectively. Bright,ductile and leveled electrodeposits of cobalt are obtained from about 10to 60 amps/sq. ft.

In the periodic reverse current processes, excellent bright deposits ofnickel, cobalt and nickel-cobalt alloys can be produced from solutionshaving brightener com pounds of this invention at concentrations as lowas 0.00005 02/ gal. and as high as 0.05 oz./ gal. The regularuninterrupted current processes employ the compounds at concentrationsfrom 0.0005 to 0.05 oz./gal., as outlined heretofore. The economics ofsuch low brightener concentrations in the periodic reverse currentprocesses are obvious.

While there have been shown and described what are presently consideredto be the preferred embodiments of the invention, modifications theretowill readily occur to those skilled in the art. It is not desired,therefore, that the invention be limited to the specific arrangementsshown and described and it is intended to cover in the appended claimsall such modifications as fall within the true spirit and scope of theinvention. We claim as our invention:

1. An acidic solution for electrodepositing a metal selected from thegroup consisting of nickel, cobalt and nickel-cobalt alloys containing asoluble salt of said metal and a brightener compound selected from thegroup consisting of dicyanoketene-ethyleneacetal and compounds havingthe formula:

NEG R NEO \R wherein R is selected from the group consisting of CR NHand NHR wherein R is an aliphatic monovalent hydrocarbon radical with 1to 3 carbon atoms, said brightener being present in a concentrationrange of from 0.00005 oz./gal. to 0.05 oz./gal. of solution.

2. An acidic solution for electrodepositing a metal selected from thegroup consisting of nickel, cobalt and nickel-cobalt alloys containing asoluble salt of said metal and dicyanoketeneethyleneacetal in :aconcentration range from 0.00005 to 0.05 oz./gal. of solution.

3. An acidic solution for electrodepositing a metal selected from thegroup consisting of nickel, cobalt and nickel-cobalt alloys containing asoluble salt of said metal and 1,1-dicyano 2,2-diaminoethylene in aconcentration range from 0.00005 to 0.05 oz./ gal. of solution.

4. An acidic solution tor electrodepositing a metal selected firom thegroup consisting of nickel, cobalt and nickel-cobalt alloys containing asoluble salt of said metal and 1,l-dicyano-2,2-ethoxyethylene in aconcentration range from 0.00005 to 0.05 02/ gal. of solution.

5. An acidic solution for electrodepositing a metal selected from thegroup consisting of nickel, cobalt and nickel-cobalt alloys containing asoluble salt of said metal and 1,1-dicyan=o-2,2-n-propylaminoethylene ina concentration range from 0.00005 to 0.05 oz./ gal. of solution.

6. A method of electrodepositing a metal selected from the groupconsisting of nickel, cobalt and nickel-cobalt alloys comprising thesteps of electrolyzing an acidic electrolyte of said metal containing abrightener compound selected from the group consisting ofdicyano-keteneethyleneacetal and compounds having the formula:

NEG R NEC/ R wherein R is selected from the group consisting of NH CRand NHR wherein R is an aliphatic monov-alent hydrocarbon radical with 1to 3 carbon atoms, said brightener compound being present in aconcentration range from 0.00005 to 0.05 oz./ga1. of solution.

7. A method in accordance with claim 6, wherein said brightener compoundis dicyanoketeneethyleneacetal.

'8. A method in accordance with claim 6, wherein said brightenercompound is 1,l-dicyano-2,2-diaminoethylene.

9. A method in accordance with claim 6, wherein said brightener compoundis 1,1-dicyano-2,2-n-propylarninoethylene.

10. A method of electrodepositing a metal selected from the groupconsisting of nickel, cobalt and nickelcobalt alloys on a membercomprising the steps of applying current to the member, While in contactwith an acidic electrolyte of said metal containing a brightenercompound selected from the group consisting ofdicyanoketeneethyleneacetal and compounds having the formula:

NEG R NEC R wherein R is selected from the group consisting of NH CR andNHR wherein R is an aliphatic monovalent hydrocarbon radical with 1 to 3carbon atoms, said bright ener compound being present in a concentrationrange from 0.00005 to 0.05 oz/gal. of solution, said current beingperiodically reversed so that the member is successively cathodic for aperiod less than two seconds, then anodic for a period /2 to of thecathodic period but not less than of a second.

11. A method in accordance with claim 10, wherein said brightenercompound is dicyanoketeneethyleneacetal.

12. A method in accordance with claim 10, wherein said brightenercompound is 1,1-dicyano-2,2-diaminoethylene.

13. A method in accordance with claim 10 wherein said brightenercompound is 1,1-dicyano-2,2-ethoxyethylene.

14. A method in accordance with claim 10, wherein said brightenercompound is 1,l-dicyano-2,2-n-propylaminoethylene.

References Cited in the file of this patent UNITED STATES PATENTS2,470,775 J ernstedt et \al May 24, 1949 2,524,010 Du Rose et al. Sept.26, 1950 2,781,306 Brown Feb. 12, 1957 2,882,208 Becking et al. Apr..14, 1959 2,972,571 Towle Feb. 21, 1961 2,978,391 Du Rose Apr. 4, 1961OTHER REFERENCES Middleton et al.: J. Am. Chem. Soc, vol. 80, pp. 2788-2795, June 1958.

1. AN ACIDIC SOLUTION FOR ELECTRODEPOSITING A METAL SELECTED FROM THEGROUP CONSISTING OF NICKEL, COBALT AND NICKEL-COBALT ALLOYS CONTAINING ASOLUBLE SALT OF SAID METAL AND A BRIGHTENER COMPOUND SELECTED FROM THEGROUP CONSISTING OF DICYANOKETENE-ETHYLENEACETAL AND COMPOUNDS HAVINGTHE FORMULA: